The plastic wrap solution is a low-cost and fairly efficient solution to imperfect windows. They seal up minor leaks around old windows, but more importantly, that cushion of air is a fairly good layer of insulation.
I mean, in an ideal world houses would not be inefficient or you would just renovate to fix them, but this world is anything but ideal and plastic wrap is cheap and effective.
Just, like, don't just get some saran wrap and go to town with it, there is proper stuff you can get for it.
